Previous architectures for interactive television systems require high-bandwidth transmission facilities to enable high-resolution images to be displayed and quick response times to be achieved during interactive sessions. This bandwidth is costly in terms of available resources and network elements involved.
Industry efforts have been directed toward developing and improving technology for storing and transporting information using an analog coaxial cable channel. A typical coaxial channel has a bandwidth of about 6 MHz, which accommodates a bit rate of up to about 28 Mbps.
The Motion Picture Experts Group (MPEG), an International Standards Organization (ISO)-sanctioned group provides a standard for full motion digital video compression. The MPEG compression standard for full motion video takes advantage of the fact that full motion video is made up of many successive frames consisting of large areas that are not changed, such as blue sky background. MPEG performs "differencing", that is noting differences between consecutive frames. If two consecutive frames are identical, the second can be stored with the appropriate information.
In server applications it is desirable to convert input data to bit sequences insertable in a bit stream for transmission. For example, according to the MPEG standard, input video data is encoded as compressed bitstreams as specified in the MPEG standard specification: MPEG TEST MODEL 4, "Coded Representation of Picture and Audio Information", ISO-IEC/JTC1/SC29/EG11, CCITT SG XV, Working Party XV/1, Document AVC-445b, February 1993.
Video data can be streamed through a coaxial cable using the MPEG-2 compression standard at a bit rate in a range from 2.5 Mbps through 6 Mbps without noticeable degradation of video imagery, and without artifacts. It is difficult to create an interactive video menu session that creates the appearance of a dedicated session using lower bit rates than that.
Previous interactive video menu architectures require large pipes (i.e., large transmission bandwidth) and costly set-top boxes (STBs) associated with the television. A larger pipe (i.e., more bandwidth) is necessary if compression of the video is performed at a higher speed. Some architectures use locally generated graphics for the background, requiring costly and more complex STBs associated with the television. As a result, there is a continuing need for a low-cost, low-memory menuing system for use in interactive television, which is able to transmit still, moving, or picture-in-picture video images using MPEG-2 compression at below 1.5 Mbps to cost-effectively minimize bandwidth, while maintaining image quality and quick response times.